Methods for the production of renewable Dimethyl JP10

ABSTRACT

A highly efficient method for the conversion of a natural product into the high density fuel RJ-4 with concomitant evolution of isobutylene for conversion to fuels and polymers, more specifically, embodiments of the invention relate to efficient methods for the conversion of the renewable, linear terpene alcohol, linalool into a drop-in, high density fuel suitable for ramjet or missile propulsion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional patent application claiming the benefit of Ser. No.13/604,115 filed on Sep. 5, 2012, which is the non-provisional patentapplication of, claiming the benefit of, parent application Ser. No.61/531,970 filed on Sep. 7, 2011, and is a continuation-in-part of,claiming the benefit of, parent application Ser. No. 12/511,796 filed onJul. 29, 2009, whereby the entire disclosure of which is incorporatedhereby reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The invention described herein may be manufactured and used by or forthe government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

FIELD OF THE INVENTION

The invention generally relates to a highly efficient method for theconversion of a natural product into the high density fuel RJ-4 withconcomitant evolution of isobutylene for conversion to fuels andpolymers.

It is to be understood that the foregoing is exemplary and explanatoryonly and are not to be viewed as being restrictive of the invention, asclaimed. Further advantages of this invention will be apparent after areview of the following detailed description of the disclosedembodiments, which are illustrated schematically in the accompanyingdrawings and in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph of the room temperature, solvent free reaction oflinalool with catalyst at five minutes after addition, according toembodiments of the invention.

FIG. 2 is a graph illustrating a GC Chromatogram of MCPD dimers derivedfrom dehydration of 1 with AlPO₄/MgSO₄ followed by ambient temperaturedimerization, according to embodiments of the invention.

FIG. 3 is a graph that is a representative ¹H NMR of1-methylcyclopent-2-enol produced by RCM of linalool, according toembodiments of the invention.

FIG. 4 is a graph showing a representative GC of the mixture in thereaction flask after RCM with Grubbs 1^(st) generation catalyst,according to embodiments of the invention.

FIG. 5 is a graph showing a representative ¹H NMR of the2-methylcyclopentadiene product from the RCM reaction, minor productsinclude 1-methylcyclopentadiene, methyl cyclopentadiene dimer, andstarting alcohols and ethers, according to embodiments of the invention.

FIG. 6 is a graph showing a representative ¹H NMR spectrum of thedehydration of 1 with the heterogeneous acid catalyst, Nafion SAC-13,according to embodiments of the invention.

FIG. 7 is a graph showing a representative GC from the reaction flaskafter dehydration with Nafion SAC-13 shows starting material, ethers,dimers, trimers, and tetramers in solution, according to embodiments ofthe invention.

FIG. 8 is a graph showing a representative GC from the reaction flaskafter dehydration with AlPO₄, according to embodiments of the invention.

FIG. 9 is a graph showing a GC of the dimer mixture after hydrogenationwith PtO₂ at 40 psi H₂, according to embodiments of the invention.

It is to be understood that the foregoing general description and thefollowing detailed description are exemplary and explanatory only andare not to be viewed as being restrictive of the invention, as claimed.Further advantages of this invention will be apparent after a review ofthe following detailed description of the disclosed embodiments, whichare illustrated schematically in the accompanying drawings and in theappended claims.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

Embodiments of the invention generally relate to a highly efficientmethod for the conversion of a natural product into the high densityfuel RJ-4 with concomitant evolution of isobutylene for conversion tofuels and polymers.

More specifically, embodiments of the invention relate to efficientmethods for the conversion of the renewable, linear terpene alcohol,linalool into a drop-in, high density fuel suitable for ramjet ormissile propulsion. In line with Navy goals, these embodiments have thepotential to decrease net carbon emissions of various platforms whilemaintaining optimum performance.

Fuels suitable for missile propulsion have multi-cyclic structures thatimpart high density while maintaining suitable low temperatureviscosity. These fuels are particularly difficult to produce fromrenewable sources given their stringent requirements. Embodiments ofthis invention describe a highly efficient method for the conversion ofthe naturally occurring terpene alcohol, linalool, into the high densityfuel RJ-4 which is composed of hydrogenated methylcyclopentadienedimers. Recent work has shown that terpene alcohols and relatedmolecules can be produced from cellulose with bioengineered organisms.In conjunction with the embodiments of this invention, this will allowfor the sustainable and renewable production of a high density fuel fromwaste biomass. In addition to the production of RJ-4, embodiments ofthis invention generate isobutylene as a side-product which can beisolated and converted to gasoline, jet fuel, or polymers/elastomers.

The ring closing metathesis (RCM) of linalool to produce1-methylcyclopent-2-enol and isobutylene using Ru-metathesis catalystshas been demonstrated in the literature. However, previous methods haveutilized elevated temperatures, dilute solutions in chloroform, and ingeneral, high catalyst loadings. This is in contrast to embodiments ofthis invention method which are performed without solvent and atloadings as low as 0.01 mol %.

Embodiments of the invention relate to a method for manufacturing highdensity fuels including, reacting at least one terpene alcohol with atleast one Ru-metathesis catalysts with a solvent or under solvent-freeconditions to produce 1-methylcyclopent-2-enol, dehydrating the1-methylcyclopent-2-enol with at least one heterogeneous dehydrationcatalyst to produce methylcyclopentadienes, thermal dimerizing of themethylcyclopentadienes to produce methylcyclopentadiene dimers,hydrogenating the methylcyclopentadiene dimers with at least onehydrogenation catalyst to produce hydrogenated methylcyclopentadienedimers, and isomerizing the hydrogenated methylcyclopentadiene dimerswith at least one Lewis acid catalyst to produce high density fuels.Other embodiments of the invention relate to a method for producingfuels and/or byproducts including, reacting at least one terpene alcoholwith at least one Ru-metathesis catalysts under solvent-free conditionsto produce isobutylene, and oligomerizing the isobutylene with at leastone oligomerization catalyst to produce at least one of the fuels and/orbyproducts selected from the group consisting of gasoline, jet fuel, andpolymers/elastomers.

Another aspect of the invention is the high density fuels, gasolineproducts, jet fuels, polymer/elastomer products, and fuel blendsproduced either by one or a combination of the methods therein. Anotheraspect of the invention relates to a method for manufacturing highdensity fuels including, reacting at least one terpene with at least oneRu-metathesis catalysts with a solvent or under solvent-free conditionsto produce 3-methylenecyclopent-1-ene, isomerizing the3-methylenecyclopent-1-ene with at least one isomerization catalyst toproduce methylcyclopentadienes, thermal dimerizing of themethylcyclopentadienes to produce methylcyclopentadiene dimers,hydrogenating the methylcyclopentadiene dimers with at least onehydrogenation catalyst to produce hydrogenated methylcyclopentadienedimers, and isomerizing the hydrogenated methylcyclopentadiene dimerswith at least one Lewis acid catalyst to produce high density fuels.

Embodiments of the invention include at least one terpene alcohol islinalool. Other embodiments include at least one Ru-metathesis catalystsis selected from the group consisting of first generation Grubbs'catalyst, second generation Grubbs', Grubbs'-Hoveyda catalyst, catalystswith electron withdrawing alkoxides and labile pyridine ligands, and anymetathesis catalyst tolerant of alcohols, including heterogeneous metaloxides and polymer supported catalysts. In embodiments, at least oneheterogeneous dehydration catalyst is selected from the group consistingof AlPO₄, Al₂O₃, silica, MgSO₄, zeolites, and molecular sieves. In otherembodiments, the thermal dimerizing method includes increasing thetemperature to accelerate the dimerization of the methylcyclopentadienesto produce methylcyclopentadienes dimers. In other embodiments, thethermal dimerizing method includes utilizing room temperature todimerize the methylcyclopentadienes to produce methylcyclopentadienedimers.

In embodiments, a Lewis acid catalyst is employed to increase the rateof dimerization of methylcyclopentadienes. In embodiments, at least onehydrogenation catalyst includes at least one of Ni, Pd, Pt, and Cu,either supported or unsupported. In embodiments, at least one Lewis acidcatalyst for isomerization of tetrahydrodimethylcyclopentadienes isselected from the group consisting of AlCl₃, ionic liquids and saltsincluding AlCl₄ ⁻ as the anion, and other homogenous or heterogeneousLewis acids. In embodiments, the high density fuels istetrahydrodimethylcyclopentadiene (RJ-4). In other embodiments, at leastone oligomerization catalyst is selected from the group consisting ofsupported polyphosphoric acid, zeolites, metal oxides, cation exchangeresins, Lewis acids, and acid clays. In embodiments, the at least oneterpene is myrcene (see Scheme 6).

Aspects of the invention relate to a highly efficient method for theconversion of a natural product into the high density fuel RJ-4 withconcomitant evolution of isobutylene for conversion to fuels andpolymers as shown in Schemes 1 and 2

The development of techniques for the efficient synthesis of customfuels and chemicals from sustainable natural feedstocks is offundamental importance to society as the direct and indirect costs ofpetroleum use continue to increase. (A. J. Ragauskas, C. K. Williams, B.H. Davison, G. Britovsek, J. Cairney, C. A. Eckert, W. J. Frederick, J.P. Hallet, D. J. Leak, C. L. Liotta, J. R. Mielenz, R. Murphy, R.Templer, T. Tschaplinski, Science 2006, 311, 484-489. b) G. W. Huber, S.Iborra, A. Corma, Chem. Rev. 2006, 106, 4044-4098. c) J. Hill, Sust.Agric. 2009, 125-139). For general transportation fuels, complexmixtures or molecules that have somewhat lower utility than petroleumbased analogs may be sufficient, however for specific applications suchas jet and missile propulsion, a more selective model that producesmolecules with defined and specialized properties is required. Wellcharacterized, single-site catalysis is the basis of elegant syntheticstrategies for the production of pure compounds. In particular,ruthenium-based olefin metathesis catalysts are known to catalyze anumber of reactions including self-metathesis, cross-metathesis, ringclosing metathesis (RCM) and ring opening metathesis polymerization(ROMP). (G. C. Vougioukalakis, R. H. Grubbs, Chem. Rev. 2010, 110,1746-1787; A. H. Hoveyda, A. R. Zhugralin, Nature 2007, 450, 243-251. c)R. H. Grubbs, Angew. Chemie Int'l. Ed. 2006, 45, 3760-3765; R. H.Grubbs, Tetrahedron 2004, 60, 7117-7140; C. Samoj

owicz, M. Bieniek, K. Grela, Chem. Rev. 2009, 109, 3708-3742). Thisfamily of catalysts is ubiquitous in the literature and has been usedfor everything from natural product synthesis to polymer chemistry. (D.E. White, I. C. Stewart, R. H. Grubbs, B. M. Stoltz, J. Am. Chem. Soc.2008, 130, 810-811; M. Arisawa, A. Nishida, M. Nakagawa, J. Organomet.Chem. 2006, 691, 5109-5121; G. O. Wilson, M. M. Caruso, N. T. Reimer, S.R. White, N. R. Sottos, J. S. Moore, Chem. Mater. 2008, 20, 3288-3297;R. M. Thomas, R. H. Grubbs, Macromolecules 2010, 43, 3705-3709.) Thetransition of these catalysts to large scale industrial processes has inthe past been hindered by their modest turnover numbers and high cost.(M. Ulman, R. H. Grubbs, J. Org. Chem. 1999, 64, 7202-7207. b) J. C.Conrad, J. L. Snelgrove, M. D. Eeelman, S. Hall, D. E. Fogg J. Molec.Catal. A 2006, 254, 105-110). To overcome these difficulties, catalyticsystems need to be developed that can efficiently yield pure productswhile maintaining low catalyst loadings. In this specification, wedetail a ruthenium catalyzed method for the synthesis ofdimethyldicyclopentadiene from linalool, a linear terpene alcohol.Recent work in our lab has focused on the conversion of terpenes to highdensity fuel surrogates. (B. G. Harvey, M. E. Wright, R. L. QuintanaEnergy Fuels 2010, 24, 267-273). Although terpenes are naturallyproduced by pine trees and a variety of plants, a truly sustainablemethod may require the utilization of bioengineered microbes to producespecific molecules or families of molecules from waste cellulose. (M. C.Y. Chang, J. D. Keasling Nature Chem. Bio. 2006, 2, 674-681; F. M.Carrau, K. Medina, E. Boido, L. Farina, C. Gaggero, E. Dellacassa, G.Versini, P. A. Henschke, FEMS Microbio. Lett. 2005, 243, 107-115).

Within the terpene family, linalool is a particularly intriguingfeedstock for fuels due to its molecular structure. Although the RCM oflinalool must proceed through a sterically hindered transition state,the reaction is facilitated by coordination of the allylic alcohol. (T.R. Hoye, H. Zhao Org. Lett. 1999, 1, 1123-1125). This results in anefficient method for the synthesis of 1-methylcyclopent-2-enol (1) andisobutylene (Scheme 2). Both of these products are of significantinterest as they can be converted to renewable fuel and polymerproducts. Isobutylene is a valuable side-product that can be selectivelytrimerized to produce jet fuel, dimerized, or alkylated with C4raffinate to produce high octane gasoline, or polymerized topolyisobutylene. (R. Alcántara, E. Alcántara, L. Canoira, M. J. Franco,M. Herrera, A. Navarro, React. Funct. Polym. 2000, 45, 19-27; J. W.Yoon, S. H. Jhung, T-J. Kim, H-D. Lee, N. H. Jang, J-S. Chang, Bull.Korean Chem. Soc. 2007, 28, 2075-2078; D. M. Haskell, F. Floyd, U.S.Pat. No. 4,301,315, 1981; T. I. Evans, L. J. Karas, R. Rameswaran, U.S.Pat. No. 5,877,372, 1999; Y. Li, Y. Wu, L. Liang, Y. Li, G. Wu, Chin. J.Polym. Sci. 2010, 28, 55-62; V. Vasilenko, A. N. Frolov, S. V. Kostjuk,Macromolecules 2010, 43, 5503-5507; Q. Liu, Yi-X. Wu, Y). Meanwhile, 1can be efficiently converted to methylcyclopentadiene dimer, which canbe hydrogenated and isomerized to produce the high density missile fuelRJ-4. (G. W. Burdette, A. I. Schneider, U.S. Pat. No. 4,398,978, 1983;J. S. Chickos, A. E. Wentz, D. Hillesheim-Cox, Ind. Eng. Chem. Res.2003, 42, 2874-2877 (Scheme 1)).

NMR scale conversions of linalool to 1 under dilute conditions and atelevated temperatures have been reported in the literature. Catalystsused for this reaction (Scheme 3) have included the first generationGrubbs' catalyst (2), both a second generation Grubbs' (5) andGrubbs'-Hoveyda catalyst (4), as well as catalysts with electronwithdrawing alkoxides and labile pyridine ligands (6,7). (D. C.Braddock, A. Matsuno, Tet. Lett. 2002, 43, 3305-3308; J. C. Conrad, H.H. Parnas, J. L. Snelgrove, D. E. Fogg, J. Am. Chem. Soc. 2005, 127,11882-11883). More recently the RCM of linalool and several othersubstrates has been studied with ruthenium catalysts functionalized withN-napthyl substituted heterocyclic carbene ligands. (L. Vieille-Petit,H. Clavier, A. Linden, S. Blumentritt, S. P. Nolan, R. Dorta,Organometallics 2010, 29, 775-788) Among these examples, the alkoxidefunctionalized catalysts are particularly notable as they were able toachieve 100% conversion in 15 min at 0.5 mol % loading and in somecases, full conversion in one h at 0.05 mol % loading in refluxingchloroform. This is in contrast to the other catalyst studies thatutilized relatively high catalyst loadings (1-5%) to achieve highconversion efficiencies (Table 1). Although these preliminary studieswere intriguing, the work in our laboratory focused on maximizing theturnover number (TON) for the RCM of linalool while reducing the use ofextraneous solvents and the energy footprint of the process (a keyrequirement for the synthesis of renewable fuels). To help accomplishthis, all of the reactions were run neat, a condition that has beenshown to be effective in promoting high TONs for certain substrates. (M.B. Dinger, J. C. Mol, Adv. Synth. Catal. 2002, 344, 671-677).

TABLE 1 Reaction conditions and yield of 1 for a series of rutheniummetathesis catalysts Loading Catalyst (mol %) Temp Time Solvent Yield 25 ambient minutes CDCl₃ 100 2 0.1 ambient 16 h neat  0 2 0.1 45  1 hneat  55 3 0.1 60 30 min neat  36 3 0.01 ambient 16 h neat  0 3 0.01 6030 min neat  18 4 0.1 ambient 45 min neat 100 4 0.01 ambient  1 h neat 44 5, 6, 7a, 0.5 60 15 min CDCl₃  100^(b) 7b, 7c 5, 6, 7a, 0.05 60  1 hCDCl₃ 24, 29, 7b, 7c 100, 17, 34

As the first step in the development of a large scale synthesis of thehigh density fuel RJ-4 from a renewable source, the solvent-free,preparative scale RCM of linalool with three commercial catalysts wasstudied. The first generation Grubbs catalyst 2, a second generationGrubbs catalyst with a sterically open N-heterocyclic carbene ligand 3,and a second generation Grubbs-Hoveyda catalyst 4 were screened foractivity. For catalyst 2, attempts to decrease the loading to 0.1 mol %resulted in incomplete conversion to the alcohol. No reaction wasobserved at room temperature, while reaction at 45° C. resulted in 55%conversion after one hour. Increasing the reaction time did not lead tofurther reaction. Catalyst 3 which was chosen based on its wellestablished activity in the RCM of sterically hindered substratesproduced no discernible product after 16 h at ambient temperature witheither 0.1 or 0.01 mol % loading, however at 60° C., yields of 36 and18% were obtained, respectively. Unfortunately, catalyst 3 deactivatedwithin 30 minutes at this temperature, a result that was not surprisinggiven the reported modest thermal stability of this catalyst. (I. C.Stewart, T. Ung, A. A. Pletnev, J. M. Berlin, R. H. Grubbs, Y. Schrodi,Org. Lett. 2007, 9, 1589-1592).

FIG. 1 is a photograph of the room temperature, solvent-free reaction oflinalool with catalyst 4 at five minutes after addition. Vigorousbubbling is due to production of isobutylene. To improve the conversionefficiency, the more stable catalyst 4 was evaluated at a loading of 0.1mol %. At room temperature the reaction proceeded rapidly (FIG. 1) withcopious production of isobutylene. By this method linalool was convertedquantitatively to 1 in 45 min at ambient temperature. At 0.01 mol %loading, a 44% conversion to the alcohol was achieved in one h,representing a remarkable TON of 4400. Reaction for longer periods oftime resulted in no improvement in yield. Based on the catalystscreening, 4 was utilized in preparative scale (30 g) syntheses of 1.Isobutylene was either collected with a dry ice condenser or allowed toescape through a bubbler. At the conclusion of the reaction, the productwas isolated by vacuum distillation at room temperature; yields of >95%were routinely achieved.

In an attempt to improve the conversion efficiencies of catalysts 2 and4, the effect of increasing the temperature was studied. Interestingly,when either 2 or 4 were used as the catalyst, a reaction temperature of60° C. resulted in partial conversion of 1 to methylcyclopentadiene(MCPD). GC/MS analysis of the reaction mixture showed that linalool hadbeen converted to a complex mixture of 1, cyclopentenol ethers, MCPD,and methylcyclopentadiene dimers (Scheme 4). In effect it appeared that2 and 4 were acting as dehydration catalysts. Interestingly, for 4, thissame effect was not observed when sufficient linalool was present insolution. As a control, a 0.01 mol % solution of catalyst 4 in linaloolwas prepared. After the reaction had proceeded to 44% conversion, themixture was heated to 60° C. for 16 h. No dehydration of the product wasobserved. It is also important to note that catalyst decomposed throughair exposure was not active for the dehydration of the alcohol. Rapidstirring of the flask in open air or alternatively active bubbling ofair into the reaction flask resulted in a color change from green tobrown-black. This oxidized mixture was much less prone to dehydrationreactions.

Although the dehydration reaction appeared to be mediated by theruthenium catalyst, another possibility is that the catalyst reactedwith linalool, 1, or water to exchange alkoxide or hydroxide ligandswith the chloride ligands. This process would release catalytic amountsof HCl which could then lead to dehydration of the alcohol. Toinvestigate the extent to which a Lewis acid would dehydrate 1, thealcohol was allowed to react with the Lewis acids PdCl₂(PhCN)₂ andRu(COD)Cl₂ at room temperature in CDCl₃. As a control, Pd(0) (5% Pd/C)was also evaluated as a catalyst for the dehydration of 1.Interestingly, all of the catalysts converted 1 to similar mixtures ofdehydrated products comparable to those observed with the metathesiscatalysts. Further observation revealed that although neat samples of 1were stable indefinitely in closed flasks at room temperature, NMRsamples in CDCl₃ slowly converted to dehydrated mixtures, albeit at amuch slower rate than for the Lewis acid catalyzed reactions. Given theknown decomposition of chloroform to produce HCl and phosgene, it seemslikely that even this small amount of acid was sufficient to promote thedehydration of the alcohol.

Scheme 4

Mechanism for the acid catalyzed dehydration of2-methyl-1-cyclopentenol.

Although the Ru-catalysts showed some modest activity for the partialdehydration of 1, more efficient and selective methods were sought toconvert 1 to MCPD. Given the rapid room temperature conversion of MCPDto dimer, particularly in the presence of acid catalysts, two distinctroutes to the dimer were conceived. In the first route, a solid acidcatalyst would be employed and the dehydration and dimerization wouldoccur in the same flask. In the second route, a dehydration catalyst ofmuch lower acidity would be employed and the reaction carried out underreduced pressure, allowing the volatile MCPD to be easily separated fromthe reaction mixture. For the first route, heterogeneous solid acidcatalysts were employed to allow for easy isolation of the product.Montmorillonite K10 (MMT-K10), an acid clay, and Nafion SAC-13, a silicasupported perfluorinated cation exchange resin were screened foractivity. Although both catalysts resulted in high conversions (95%conversion in one hour at ambient temperature), both yielded complexmixtures consisting of ether, dimer, significant amounts of trimer, andother heavier oligomers (Table 2). To try and trap MCPD prior tooligomerization, the reaction was conducted with Nafion SAC-13 at 40° C.under reduced pressure (40 torr). Although the isolated MCPD was >90%pure, the yield was low and the reaction mixture rapidly oligomerized toa thick orange oil composed of heavy oligomers. From this result it wasclear that in the case of strong heterogeneous acid catalysts,oligomerization occurred more rapidly than MCPD could be removed fromthe reaction flask.

To further investigate optimal dehydration conditions, a series of weakBronsted and Lewis acid catalysts were screened to determine theiractivity in the selective dehydration of 1 (Table 2). Benzoic acid anddilute HCl were unselective and produced primarily ether along withdimer and trimer. Surprisingly, Pd(COD)Cl₂ reacted almost quantitativelyand produced 66% dimer along with significant amounts of trimer andtetramer. In the search for a milder dehydrating agent, magnesiumsulfate was employed as a catalyst and produced only ethers. In contrastto the other dehydration catalysts that produced primarily one etherisomer, MgSO₄ produced the two distinguishable ether isomers in nearlyequal amounts. This difference in isomer distribution is attributed tothe lack of suitable acid sites on the catalyst. In the absence of thesesites the reaction is driven by the coordination of water to magnesiumcations and is dependent on the auto-ionization of the alcohol. Based onthese initial screening results, an aluminum phosphate catalyst wasprepared and evaluated as a dehydration catalyst. (A. W. Wang, FinalReport US Department of Energy, Contract No. DE-FC22-94PC93052, 2002).Under a variety of conditions, this catalyst was selective for theproduction of only ethers, MCPD, and dimers; no heavier oligomers wereformed. Despite the favorable product distribution, the conversionefficiency of this catalyst was limited by the production of water inthe dehydration reaction. To overcome this hurdle, mixtures of AlPO₄with a suitable drying agent were employed. An AlPO₄/molecular sievecatalyst resulted in a low overall yield of MCPD with formation of anoligomeric mixture. In contrast, an AlPO₄/MgSO₄ catalyst permitted thedirect conversion to MCPD. The optimized catalyst allowed for a 78%isolated yield of isomeric MCPD from 1.

TABLE 2 Catalysts for the dehydration of 1 Products 1:ether:dimer:Catalyst Temp Time Pressure oligomer MMT-K10 25  1 h atm  5:41:22:32Nafion SAC-13 25  1 h atm  6:35:23:36 Pd(COD)Cl₂ 25 16 h atm <1:14:66:232M HCl 25  1 h atm  0:(86):13^(a) MgSO₄ 25 16 h atm 16:84:0:0 BenzoicAcid 25 16 h atm  8:66:21:4 AlPO₄/MgSO₄ 60  5 h 40 torr 10:90:0:0^(b)^(a)The number in parantheses is the mass % of ethers and dimerscombined. ^(b)This distribution represents what was left in the reactionflask. A 78% isolated yield of MCPD isomers was obtained through thismethod.

FIG. 2. GC Chromatogram of MCPD dimers derived from dehydration of 1with AlPO₄/MgSO₄ followed by ambient temperature dimerization.

The dimer product distribution resulting from the room temperatureDiels-Alder cycloaddition of MCPD is of significant interest and isin-part controlled by the starting composition of MCPD isomers.Dehydration of the alcohol with AlPO₄ at 60° C. yields 84%2-methylcyclopentadiene (8) and 16% 1-methylcyclopentadiene (9), while5-methylcyclopentadiene was not observed. The predominance of 8 resultsfrom the formation of a more stable tertiary carbocation compared to thesecondary carbocation intermediate required for 9 (Scheme 4). Incommercial methylcyclopentadiene dimer, seven peaks are observed in thegas chromatogram. (M. A. Diez, M. D. Guillen, C. G. Blanco, J. Bermejo,J. Chromatography 1990, 508, 363-374.) The distribution contains fourmajor peaks representing various isomers resulting from thecycloaddition of 2-methyl and 1-methyl cyclopentadiene. The dimers arepresent almost exclusively as the endo isomers. In the current work,seven peaks are observed, however the distribution is significantlydifferent than for the commercial product, with two peaks representing88% of the dimers. The largest peak (56%) is observed for3,9-dimethyl-endo-tricyclo[5.2.1.0^(2,6)] deca-3,8-diene (10), while theother main peak (33%) is observed for4,9-dimethyl-endo-tricyclo[5.2.1.0^(2,6)] deca-3,8-diene (11) (Scheme5). In comparison, the commercial product is 36% 10 and 29% 11. (W.Thommen, H. Pamingle, K. H. Schulte-Elte, Helv. Chim. Acta 1989, 72,1346-1353). Coupling of two molecules of 8 yields 10, while coupling of8 and 9 yields 11. The distribution of isomers is also dependent on boththe relative dimerization rates of 8 and 9 as well as concomittantmonomer isomerization. Previous studies have shown that2-methylcyclopentadiene dimerizes faster than 1-methylcyclopentadieneostensibly due to less steric crowding at the site of cycloaddition;this effect further influences the final distribution. (S. M. CsicseryJ. Org. Chem. 1960, 25, 518-521).

Interestingly, dimer 12 which represents roughly 10% of commercialdimethyldicyclopentadiene is only 3% of the current mixture. This islikely the result of the known [3,3]-sigmatropic Woodward-Katzrearrangement to 11 being catalyzed by the dehydration conditions. (W.Thommen, H. Pamingle, K. H. Schulte-Elte, Helv. Chim. Acta 1989, 72,1346-1353).

Scheme 5

Prominent endo-isomers produced from the thermal dimerization of MCPDisomers derived from 2-methyl-1-cyclopentenol. The first number of apair represents the % composition produced in this work, while thenumbers in brackets refer to % composition of the commercial product.

Scheme 6.

In order to convert the dimer mixture to RJ-4, it must first behydrogenated. This was accomplished under mild conditions (40 psi, PtO₂catalyst) and resulted in six distinguishable isomers. The four majorpeaks representing 91% of the product are the four sets of diasteriomersarising from the non-stereospecific hydrogenation of 10 and 11. Afterhydrogenation, these mixtures can be isomerized with strong Lewis acidcatalysts to fuels rich in exo-isomers.

In summary, a highly efficient and selective synthesis for theconversion of linalool to specialized fuel products has been developed.The optimized approach offers a high catalyst turnover number, solventfree conditions, low external energy demands, and an exceptionally welldefined product distribution. Further work to effectively reducecatalyst loadings and to establish how the distribution of dimers willaffect the performance of high density fuel mixtures is ongoing.

EXPERIMENTAL SECTION

General: Grubb's 1^(st) generation catalyst (2), Grubb's 2nd generationcatalyst (3), and Grubb's-Hoveyda 2^(nd) generation catalyst (4), werepurchased from Aldrich, stored in a nitrogen filled glove box, and usedas received. Linalool (97%, FG) was purchased from Aldrich and wasdistilled under reduced pressure and stored under nitrogen before useunless otherwise noted. MgSO₄ (Polarchem), 4 Å molecular sieves(Aldrich), MMT-K10 (Aldrich), Nafion SAC-13 (Aldrich), benzoic acid(Aldrich), Al(NO3)₃-9H₂O (RG Aldrich), H₃PO₄ (85%, Fisher), and NH₄OH(27%, Aldrich) were used as received. ¹H NMR measurements were performedusing a Bruker AC 200 instrument. ¹H NMR chemical shifts are reportedversus the deuterated solvent peak (CDCl₃, δ 7.25 ppm). Product mixtureswere analyzed with an Agilent 6890-GC system with a Restek RTX-5MS30-meter column. The GC inlet temperature was 250° C. and the columnoven temperature was initially held at 40° C. for three minutes and thenincreased to 350° C. at 10° C./min. An Agilent mass selective detector(MSD) 5973 system was used to identify the sample's components.

Example 1, General Preparative Scale Procedure for Synthesis of 1 fromLinalool

Reactions were run with 0.1 mol % of the Hoveyda-Grubbs 2^(nd)generation catalyst. The catalyst was stored in the glove box and therequired amount was removed in a round bottom flask charged with astirbar, and sealed with a septum. Linalool was transferred via syringeinto the RBF containing the catalyst. At this point the flask was ventedthrough an oil bubbler and within 30 seconds vigorous bubbling beganwhile stirring at room temperature. The bubbling continued for 30-45minutes and then ceased. Once bubbling had stopped air was bubbled intothe reaction mixture for 15 minutes to ensure the catalyst was inactive.¹H NMR of the crude reaction mixture showed 100% conversion of startinglinalool. The product was immediately vacuum transferred (1 torr) to achilled flask (−78° C.). After transfer the product was sealed undernitrogen and stored at room temperature. The product was analyzed viaNMR. ¹H NMR (CDCl₃) δ: 1.29 (s, 3H), 1.84 (m, 2H), 2.23 (m, 1H), 2.37(m, 1H), 2.57 (broad s, 1H), 5.65 (m, 2H). FIG. 3. Representative ¹H NMRof 1-methylcyclopent-2-enol produced by RCM of linalool.

Example 2, RCM with Grubbs' 1^(st) Generation Catalyst (2)

Grubbs' 1^(st) generation catalyst (2) (26 mg, 0.1 mol %) was placed ina 25 mL round bottom flask charged with a Teflon stirbar. The flask wassealed with a septum and removed from the glove box. The flask wasplaced in an oil bath and held at 45° C. To this flask 5 mL of distilledlinalool was added via syringe and the reaction was vented to an oilbubbler. Within 5 minutes slow bubbling was seen in the oil bubbler, butno bubbling was seen in the reaction flask. At 45 minutes bubbling beganin the reaction flask and ceased completely at 90 min. ¹H NMR showed 55%conversion of the starting linalool. FIG. 4. A representative GC of themixture in the reaction flask after RCM with Grubbs 1^(st) generationcatalyst. The peak with RT=10.51 represents unreacted linalool.Significant dehydration products are present with very littlemethylcyclopentenol (RT ˜6 min) present.

Example 3, RCM with 2^(nd) Generation Grubbs (3)

2^(nd) generation Grubbs catalyst (3) (12 mg, 0.1 mol %) was placed in a25 mL round bottom flask charged with a Teflon stirbar. The flask wassealed with a septum and removed from the glove box. The flask wasplaced in an oil bath and held at 60° C. To this flask, 3 mL ofdistilled linalool was added via syringe and the reaction was vented toan oil bubbler. Within 5 minutes bubbling was seen in the flask and thiscontinued for 20 minutes after which bubbling ceased. ¹H NMR taken at 30min showed 36% conversion of the starting linalool. A spectrum at 3 hshowed no further conversion.

Example 4, Dehydration Catalyst Screening

Unless otherwise noted all of the dehydration test reactions werecarried out at room temperature with stirring in air. The dehydratingagent was added to 1 mL of 1 in a vial and stirred. Crude products wereanalyzed by ¹H NMR and GC-MS.

-   -   Nafion SAC-13: 50 mg of Nafion Sac-13 was added and the reaction        was stirred for 1 h. ¹H NMR showed only a small amount of the        starting alcohol and no methylcyclopentadiene. Analysis by GC-MS        gave 6% 1, 35% ethers, 23% dimers, 28% trimers and 9% tetramers.    -   MMT-K10: 50 mg of MMT-K10 was added and the reaction was stirred        for 1 h. ¹H NMR showed only a small amount of the starting        alcohol and no methylcyclopentadiene. Analysis by GC-MS gave 5%        1, 41% ethers, 22% dimers, 28% trimers and 4% tetramers.    -   HCl: 1 mL of 2M HCl was added and the reaction was stirred for 1        hour. ¹H NMR at 1 h showed no starting alcohol and no        methylcyclopentadiene. Analysis by GC-MS gave a complex mixture        of ethers, and dimers making up 86% of the sample with an        additional 12% trimers and 1% tetramers.    -   Benzoic Acid: 50 mg of benzoic acid was added and the reaction        was stirred for 1 hour. The NMR showed no reaction at 1 hour and        the solution was left to stir overnight. ¹H NMR at 20 h showed        only a small amount of the starting alcohol, and no        methylcyclopentadiene. Analysis by GC-MS gave 8% 1, 66% ethers,        22% dimers and 4% trimers.    -   Magnesium Sulfate: 150 mg of MgSO₄ was added and the reaction        was stirred for 1 h. ¹H NMR showed no reaction and the mixture        was left to stir overnight. ¹H NMR at 24 h showed significant        amounts of the starting alcohol, and no methylcyclopentadiene;        the reaction was stopped at this point. Analysis by GC-MS gave        16% 1 and 84% ethers. No conversion to methylcyclopentadiene or        heavier products was observed.    -   Pd(COD)Cl₂: 50 mg of Pd(COD)Cl₂ was added and the reaction was        stirred for 1 h; ¹H NMR taken at this point showed no        significant conversion and the solution was left to stir        overnight. ¹H NMR at 24 hours showed no starting alcohol, and no        methylcyclopentadiene. Analysis by GC-MS gave <1% 1, 14% ethers,        66% dimers, 16% trimers, and 7% tetramer.    -   Aluminum Phosphate with 4 Å Mol. Sieves: 310 mg of AlPO₄ and 500        mg of 4 Å molecular sieves were added. This flask was placed in        a 60° C. oil bath and 6 mL of 1 was added via syringe. The        desired methylcyclopentadiene was obtained through distillation        under vacuum (˜40 torr). The receiving flask was placed in dry        ice to ensure no loss of product. The reaction ran for 8 hours        and only ˜100 μL was collected in the receiving flask. ¹H NMR of        this portion showed a mixture of 1-methylcyclopentadiene and        2-methylcyclopentadiene in a 1:3 ratio, respectively. The        reaction flask was a thick orange oil and was not analyzed        farther.

Example 5, Preparation of AlPO₄

This synthesis was adapted from a literature procedure. Aluminum nitratenonahydrate, Al(NO₃)₃.9H₂O, (16.0 g, 43 mmol) was dissolved in 75 mL ofDI water. 3 mL of 85% H₃PO₄ was added dropwise with rapid stirring. 13mL of 27% NH₄OH was diluted in 30 mL of DI water and then this dilutedsolution was slowly added dropwise to the reaction mixture. Onceaddition was complete a thick white precipitate had formed and anadditional 20 mL of DI water was added to allow for continued stirringof the mixture. The slurry was left to stir for 20 hours after whichtime the solution was filtered. The resulting solid was re-dispersed in100 mL of DI water and stirred for 1 hour. The mixture was thencentrifuged and the water was decanted. The solid was dried overnight at120° C. in a vacuum oven. The white solid was powdered using a mortarand pestle to yield 4.78 g of white solid.

Example 6, Dehydration with AlPO₄ & MgSO₄

AlPO₄ (1.34 g, 11 mmol) and MgSO₄ (1.63 g, 13 mmol) were placed in a 50mL round bottom flask charged with a stirbar. To this flask 1 (13.01 g,0.13 mol) was added, and the flask was fit with a small distillationhead. The receiving flask was placed in a dry ice bath and the reactionwas placed under vacuum (40 torr). The reaction was run at 60° C. for 5hours. Total yield of the distillate was 78%. ¹H NMR for the majorproduct, 2-methylcyclopentadiene (CDCl₃) δ: 2.06 (s, 3H), 2.98 (s, 1H),6.04 (s, 1H), 6.44 (s, 2H).

FIG. 5. Representative ¹H NMR of the 2-methylcyclopentadiene productfrom the RCM reaction, minor products include 1-methylcyclopentadiene,methyl cyclopentadiene dimer, and starting alcohols and ethers. FIG. 6.A representative ¹H NMR spectrum of the dehydration of 1 with theheterogeneous acid catalyst, Nafion SAC-13. FIG. 7. A representative GCfrom the reaction flask after dehydration with Nafion SAC-13 showsstarting material, ethers, dimers, trimers, and tetramers in solution.FIG. 8. A representative GC from the reaction flask after dehydrationwith AlPO₄. The only major peaks observed are for starting material andethers; no heavier product formation is observed.

Example 7, Hydrogenation of MCPD Dimers

8 g (0.1 mol) of MCPD dimers were diluted with 20 mL THF. PtO₂ (80 mg,0.35 mmol) was added to the mixture which was then transferred to asmall Parr hydrogenation apparatus under 40 psi H₂ with shaking. Thepressure was monitored and held between 30-40 psi for the duration ofthe reaction. After 20 hours H₂ was no longer being consumed and thereaction was stopped. The excess H₂ was removed under reduced pressureand the platinum catalyst was removed by filtration through a plug ofglass wool. THF was removed under reduced pressure to yield a mixture ofhydrogenated MCPD dimers which were subsequently analyzed by GC-MS. FIG.9. GC of the dimer mixture after hydrogenation with PtO₂ at 40 psi H₂.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassedwithin the invention. The upper and lower limits of these smaller rangesmay independently be included or excluded in the range, and each rangewhere either, neither or both limits are included in the smaller rangesis also encompassed within the invention, subject to any specificallyexcluded limit in the stated range. Where the stated range includes oneor both of the limits, ranges excluding either or both of those includedlimits are also included in the invention.

It is to be understood that the foregoing is exemplary and explanatoryonly and are not to be viewed as being restrictive of the invention, asclaimed. Further advantages of this invention will be apparent after areview of the following detailed description of the disclosedembodiments, which are illustrated schematically in the accompanyingdrawings and in the appended claims.

While the invention has been described, disclosed, illustrated and shownin various terms of certain embodiments or modifications which it haspresumed in practice, the scope of the invention is not intended to be,nor should it be deemed to be, limited thereby and such othermodifications or embodiments as may be suggested by the teachings hereinare particularly reserved especially as they fall within the breadth andscope of the claims here appended.

What is claimed is:
 1. A method for producing fuels and/or byproducts,comprising: reacting linalool with at least one ruthenium ring closingmetathesis catalyst under solvent-free conditions to produce isobutyleneand 1-methylcyclopent-2-enol; removing said isobutylene by distillationto obtain said 1-methylcyclopent-2-enol in >95% yield; and oligomerizingsaid isobutylene with at least one oligomerization catalyst to produceat least one of the fuels and/or by-products selected from the groupconsisting of gasoline, jet fuel, and polymers/elastomers.
 2. The methodaccording to claim 1, wherein said at least one ruthenium ring closingmetathesis catalyst is selected from the group consisting of firstgeneration Grubbs' catalyst, second generation Grubbs', Grubbs'-Hoveydacatalyst, and catalysts with electron withdrawing alkoxides and labilepyridine ligands.
 3. The method according to claim 1, wherein said atleast one oligomerization catalyst is selected from the group consistingof supported polyphosphoric acid, zeolites, metal oxides, cationexchange resins, Lewis acids, and acid clays.
 4. A gasoline productproduced by the method of claim
 1. 5. A jet fuel product produced by themethod of claim
 1. 6. A polymer/elastomer product produced by the methodof claim
 1. 7. A fuel blend produced by combining said high densityfuels produced by the methods of claim 1 and said fuels produced by themethods of claim 1.